Forming projections on tubes



1967 R. E. MONROE ETAL 3,354,290

FORMING PROJECTIONS ON TUBES Filed April 6, 1965 3 Sheets-Sheet 1 F g-Fig- 1 15 7?] INVENTORS 1206 era! 5. jyarrroe' ulzius Va i BY J j Nov.21, 1967 R. E. MONROE ETAL 3,354,290

FORMING PROJECTIONS ON TUBES 3 Sheets-Sheet 2 Filed April 6, 1965 T 4 fi Z a Z OWL Nov. 21, 1967 R. E. MONROE E'TAL 3,354,290

FORMING PROJECTIONS ON TUBES Filed April 6, 1965 3 Sheets-Sheet 5 UnitedStates Patent 3,354,290 I FORMING PROJECTIONS 0N TUBES Robert E. Monroeand Julius J. Vagi, Columbus, Ohio, assigno'rs to the United States ofAmerica as represented by the United States Atomic Energy CommissionFiled Apr. 6, 1965, Ser. No. 446,134 2 Claims. (Cl. 219-152) ABSTRACT OFTHE DISCLOSURE Apparatus for forming a projection on a tube byelectrical-resistance heating and pressure. External projections onzirconium-alloy tubes used as jackets of nuclearfuel elements space thefuel elements from one another. The projections are formed by theconcave recessed end of a Water-cooled copper-alloy electrode supplyingpres sure and alternating current of high amperage and low voltage tothe tube for a short time.

Contractual origin of the invention The invention described herein wasmade in the course of, or under, a contract with the US. Atomic EnergyCommission.

This invention relates to the forming of projections on a metal piece byelectrical resistance. More specifically, the invention relates to theforming of external projections on a refractory metal tube byelectric-resistance heating and shaping.

In the nuclear-reactor field it is known to provide a plurality ofrod-like fuel elements in a closely spaced parallel arrangement by meansof spiral wires applied to the exteriors of the corrosion-resistanttubes jacketing the fuel elements. Various difficulties are encountered.in the application and use of the spiral spacing wires on the fuelelements. We .propose to form short localized spacing projectionsdirectly on the tubes from the tubes themselves. The dif- .ficultyarising from such a procedure lies in the fact that the material such asa zirconium alloy suitable for jacket tubesin a nuclear reactor has ahigh melting point and is difficult to shape without damage to its ownmetallic structure.

According to the :present invention, a zirconium-alloy tube on whichprojections are to be formed is supported internally on an expandablecooled copper-alloy mandrel and is pressed externally by a concaverecessed end of a cooled dipper-alloy electrode. An alternating currentof high amperage and low voltage is applied for a short time betweenthe-electrode and mandrel across the :region of the tube wall where aprojection is to be formed. The electrode is pressed against the tubewall for a short time that is somewhat longer than that during which theelectric current is :permitted'to flow. An exterior projection is formedon the tube by flowing of metal of the tube wall into the recess-in theend of the'elcctrode.

In the drawings:

FIG. 1 is a perspective view of an electrode of the present inventionshowing the shaping end thereof;

FIG. 2 is aside view of theelectrode;

FIG. 3 is an elevation of the electrode;

'FIG. 4 is alongitudinal sectional'viewof the electrode taken on line'44of FIG. 2;

FIG. 5 is a longitudinal sectional View of theelectrode -takenonline'5-'5 ofFIG. 3;

FIG. dis a longitudinal sectional view of the mandrel of the presentinvention used to support a tubeinternally during shaping thereof;

FIG. 7 is a transverse sectional view of the mandrel taken on line 77 ofFIG. 6;

3,354,290 Patented Nov. 21, 1967 FIG. 8 is a perspective view of theentire apparatus that includes the shaping electrode and the mandrel ofthe present invention;

FIG. 9 is a fragmentary perspective view of said apparatus;

FIG. 10 is a fragmentary sectional view showing a tube to be shaped andthe shaping electrode before application thereof to the tube;

FIG. 11 is a sectional view similar to FIG. 10 after application of theelectrode to the tube; and

FIG. 12 is a fragmentary sectional view showing a pro jection formed ona tube by the apparatus of the present invention.

As shown in FIGS. 1-5, inclusive a copper-alloy electrode 10 is ofcircular cylindrical shape and has at one end two conical surfaceportions 11, two circularly cylindrical convex surface portions 12, acircularly cylindrical concave surface portion 13, and a recess 14formed in the surface portion 13. The conical surface portions 11 areformed about the axis of the electrode 10 by chamfering and areseparated from one another by the convex surface portions 12. Thesurface portions 12 are formed by a machining operation subsequent tothe chamfering operation about an axis perpendicular to the axis of theelectrode 10 and are spaced from one another by the coucave surfaceportion '13. The surface portion 13 is formed in a machining operationsubsequent to the operation forming the convex surface portions '12,about an axis perpendicular to the axis of the electrode 10, so as to betangent to the original flat end of the electrode. Sharp edges at theintersections of the surface portion '13 with the surface portions 12are removed by manual smoothing. Finally, the recess 14 is formed bypressing of a hardened drill rod against the concave surface portion13,, and the disturbed metal around the recess 14 is machined. Theinternal corners of the recess 14 are formed on a radius, rather thansharp. The recess 14 is longer than it is wide, and its length extendsparallel to the axis of the concave surface portion 13.

As shown in FIGS. 4 and 5, the electrode 10' is cooled by a coolant suchas water entering through a line 14a inserted through the end of theelectrode opposite that provided with the surfaces 11, 12, and 13. Thecoolant leaves the line 14a at .its open end and flows back and out ofthe electrode in an annular space between the .line 14a and a closed-end'bore 14b formed in the electrode and loosely containing the line 14a.

As shown in FIGS. 6 and 7, a mandrel 15 comprises a copper-alloy sleeve16, a copper-alloy tube 17, a stainless-steel rod 18, a stainless-steelstationary wedge 19, a stainless-steel adjustable wedge 20, .and astainless-steel nut 21 fixedly inserted in the wedge '20 and engaging athreaded portion 22 in one end of the rod 18. The wedges 19 and 20engage the interior of one end of the sleeve 16 which end hasdiametrally opposed .slots 23. The stationary wedge 19 is fixed andsealed to the sleeve 16. The wedge 19 is sealed to, andhas a threadedconnection with, the tube 17. The rod 18 is fixed against longitudinalmovement with respect to the stationary wedge 19 and the tube 17 by ashoulder 24 on the rod and a collar 25 secured inside the tube. Theadjustable wedge '20 .is free to move longitudinally with respect to thesleeve 16 and is prevented from rotating by engagement of an inclinedsurface 26 on the adjustable wedge with an inclined sur- "face 27 on thestationary wedge 19. When the rod ,lSis rotated by manipulation ofa'knurled'knob 28 on the end of the rod remote from the threaded portion22, the adjustable wedge 20 is moved lengthwise of the sleeve ,16 withrespect to the stationary "wedge '19, since neither the wedge 20 nor thenut 21 attached thereto can rotate. Movement of wedge 20 to the right asviewed 'in FIG. 6 acts through engagement of inclined surfaces 26 and 27to expand the mandrel or more particularly the end of the sleeve 16having the slots 23 for internal-gripping purposes. For release of themandrel 15 from gripping, the rod 18 is rotated so as to move theadjustable wedge to the left as viewed in FIG. 6.

Between the sleeve 16 and the tube 17 there is an annular space 29through which a liquid coolant such as water flows to the left as viewedin FIG. 6 after having entered the annular space 29 from an inlet line30 which is connected to the sleeve 16 near its end that appears at theright in FIG. 6. The coolant leaves the annular space 29 by way of sideopenings 31formed in the tube 17 near its end connected with thestationary wedge 19. The coolj ant, on passing through openings 31,enters an annular space 32 formed between the tube 17 and the rod 13.The coolant flows in the annular space 32 to the right as viewed in FIG.6 and leaves through an outlet line 33 connected to the end of the tube17 adjacent the knob 28. The end of the rod 18 carrying the knob 28extends from the tube 17 through an internal collar 34 with which therod has rotational sealing engagement. The adjacent ends of the sleeve16 and the tube 17 are held in spaced relation to one another by an endcap 35 which closes the adjacent end of the annular space 29. The endcap 35 is fixed to the sleeve 16 and tube 17 by set screws 36 and 37.

As shown in FIGS. 8 and 9, the apparatus of which the electrode 10 andthe mandrel 15 form part is a 50 kva. single-phase 60-cycle alternatingcurrent spot welder, although the apparatus is not used in the presentinvention for welding, but for shaping. The end of the mandrel 15adjacent the knob 28 is carried in a bracket 38 carried on a horizontalmember 39 which is carried on the upper end of a post 40 and braced by adiagonal member 41 connected with the lower end of the post. A tube 42to be shaped is applied to the end of the mandrel 15 remote from theknob 28 and rests in a horizontal insulating trough 43 carried by thehorizontal member 39. The electrode'10 is fixedly carried in a sleevemember 44 attached to a plunger 45, which is connected to a piston (notshown) shiftable in an hydraulic cylinder 46.

The tube 42 is placed on the mandrel 15, with the portion of the tube tobe processed located on the end of the sleeve 16 which has slots 23. Thegrip of the mandrel 15 is tightened by turning of rod 18 and theresultant shifting of the adjustable wedge 20. Now the electrode 10 ismoved down against the tube 42 and pressed thereagainst with anappreciable force for a short time, and during a part of this time analternating current is applied between the electrode 1 and the sleeve 16of the mandrel 15 through the region of the tube 42 lying therebetween.As a result of the intense heat generated in this region of the tube 42and the pressure applied thereagainst, there are, as shown in FIGS. 11and 12, a thinning of the tube at this region contacted by the electrodeand a thickening of the tube into a projection 47 formed in anddetermined by the recess 14 in the electrode 10. T heprojection 47 isparallel to the tube 42. The cooling water applied to the electrode 10and the mandrel and the heat conductivity of these parts due to thelarge amount of copper present in them keep electrode and mandrel coolenough to resist deformation during the shaping operation. Otherprojections 47 are formed on the tube 42 by repetition of theapplication'of pressure and electric current to the tube 42 afterrelease of the tube 42 by the mandrel, shifting of the tube on themandrel, and retightening of the mandrel. I

Successful results were achieved with the apparatus of the presentinvention in the forming of external projections on tubes 42 formed ofan alloy composed of 1.10- 1.70% by weight tin, 0.l20.18% by Weightiron, 0.05- 0.15% by weight chromium, and the remainder substantiallyall zirconium, the tube 42 having an outer diameter of l and a wallthickness of 0.056". The electrode 10 used was formed of an alloycomposed of 5 7% by weight of chromium and the balance substantiallyallcopper, having a Rockwell hardness of 83B and an electricalconductivity of 85% (I.A.C.S.) and being of RWMA Class 2. An example ofsuch an alloy is Mallory 3, manufactured by Mallory Metallurgical Co.,Indianapolis, Indiana. The electrode 10 had a diameter of A3"; conicalsurface portions 11 formed in'a 45 chamfer so as to reduce the width ofthe electrode to at the widest portion of the concave surface portion 13as viewed in FIG. 2; a radius of for the concave surface portion 13; aradius of /3" for the convex surface portions 12; and length, width, anddepth of .125, .062", and .032", re spectively, for the recess 14 in theelectrode. The sleeve 16 and tube 17 of mandrel 15 were formed of a hardcopper alloy, an example of which is one composed of 1.0% by weight ofcadmium and the balance substantially copper, having a Rockwell hardnessof 70B and an electrical conductivity of (I.A.C.S.) and being of RWMAClass 1, such as Elkaloy A, manufactured by Mallory Metallurgical Co.The forming load was 500 lbs. The current setting was 25,000 amperes.The actual current was 12,00014,000 amperes, and the actual voltage,4.2-4.5 volts. The heating time was 3 cycles. The time for applying loadwas 60 cycles.

The electrode 10 may also be formed of an alloy composed of 1-3% byweight beryllium, 5% cobalt, and the balance substantially all copper.

The tube 42 may also be so processed that the projections 47 extendother than parallel to the tube 42. This is accomplished by angularshifting of the electrode 10 about its own axis in the sleeve member 44or by a forming of the electrode so that the recess 14 therein does notextend parallel to the axis of the surface portion 13.

It is understood that the invention is not to be limited by the detailsgiven herein but that it may be modified within the scope of theappended claims.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. A method for forming an exterior short localized projection on azirconium-alloy tube, said method comprising supporting the tube on "awater-cooled copperalloy mandrel directly engaging the interior of thetube, applying with appreciable pressure for a short time against theexterior of the tube a water-cooled copperalloy electrode having aconcave cylindrical surface portion having a recess, the said surfaceportionengaging the tube exterior, and applying for a shorter time analternating current of low voltage and high amperage between theelectrode and the mandrel across the tube to form the said projection onthe tube by thinning of the region of the tube wall engaged by the saidsurface portion of the electrode and flowing and thickening of the tubewall in the said recess in the said surface portion, the said thinning,flowing, and thickening of the tube wall being due to pressure againstand electrical-resistance heating of the tube wall.

2. The method specified in claim 1, 5000 lbs. of pressure being appliedby the electrode against the tube for 60 cycles, the current being at 60cycles and having a value of 12000 to 12400 amperes at 4.2 to 4.5 voltsapplied for 3 cycles, the tube having an outer diameter of 1" and a wallthickness of .056.

References Cited UNITED STATES PATENTS 1,261,943 4/1918 Lashar 2l9-911,435,919 11/1922 Fay 219 1,504,367 8/ 1924 Meadowcroft 219-91 1,607,26211/1926 Ledwinka 219-91 2,989,618 6/1961 French 21991 X RICHARD M. WOOD,Primary Examiner.

ANTHONY BARTIS, Examiner.

B. A. STEIN, Assistant Examiner.

1. A METHOD FOR FORMING AN EXTERIOR SHORT LOCALIZED PROJECTION ON AZIRCONIUM-ALLOY TUBE, SAID METHOD COMPRISING SUPPORTING THE TUBE ON AWATER-COOLED COPPERALLOY MANDREL DIRECTLY ENGAGING THE INTERIOR OF THETUBE, APPLYING WITH APPRECIABLE PRESSURE FOR A SHORT TIME AGAINST THEEXTERIOR OF THE TUBE A WATER-COOLED COPPERALLOY ELECTRODE HAVING ACONCAVE CYLINDRICAL SURFACE PORTION HAVING A RECESS, THE SAID SURFACEPORTION ENGAGING THE TUBE EXTERIOR, AND APPLYING FOR A SHORTER TIME ANALTERNATING CURRENT OF LOW VOLTAGE AND HIGH AMPERAGE